2nd update further down.

Hi gang. *update* 19/5/08 on the bottom of this page.

I have a modified 95 Monster, running 2v 900 SuperSport motor. It has gone threw 2 new sprags in about 500Ks. The last one lasted just 15 odd starts and now it slips.
The old one came out (with a little help) in pieces. Don't know the fate of the new one yet. The bike (did) start with some choke and about 3 or 4 cranks of the motor and maybe a 2nd attempt. Im sure Im not flodding it, hence doubt any form off hydraulic lock. Starter motor wont turn the engine over now even with the plugs out, sprag just slips. You can hear the stater motor turn.
Compression is good at about 130 psi in each cylinder. Static timing is good. Recent oil/filter change, plugs, IgniTech ingniton, new belts & shims.
I have 'heard' about the removal off the spring and shortening it. Can anyone shed more light on this?

What other things could cause such premature sprag ware?

Is there a possibility of oil hydraulic-lock by the oil/pump?

Is there an alternative sprag than the OEM unit?

Push starting is out the question at the moment.

Any advice would be great, thank you . - Chris

engine won't turn over? Stupid question, it isn't in gear is it? A friend blew his starter up because the sprag never disengaged, and kept spinning the starter during a ride...8500rpm!

http://ccrma.stanford.edu/~peer/Duc/duc-spragSpring.html

not sure if that write up will help, but something is fishy if you can't turn the engine over by hand when the plugs are out.
As far as sprag wear, i am not much help there. Is it possible that the sprag clutch surface is worn and allowing the sprag to slide? Either way you are going to need to remove the cover to get a good look at it.

Good luck,
RB

RB, i think he means the engine won't turn over with the starter now.

But, sydmonster, is that correct?
Engine will still turn over by hand?

Possibly the starter gear, that goes on the inside of the sprag, is the culprit.
Maybe enough wear (on the face that engages the sprag) that it's killing 'em.

AFAIK, there's no alternative sprag, but that doesn't make it true.

I don't think there's any connection to the oil pump as far as the cause.

How many miles on the motor?

Quote from: Speeddog on May 07, 2008, 08:53:21 AM
RB, i think he means the engine won't turn over with the starter now.

so i said:

Quote from: RB on May 07, 2008, 05:51:07 AM
engine won't turn over? Stupid question, it isn't in gear is it? A friend blew his starter up because the sprag never disengaged, and kept spinning the starter during a ride...8500rpm!

but something is fishy if you can't turn the engine over by hand when the plugs are out.

So maybe i wasn't exactly clear.

What i was trying to say was, if the starter never disengaged the inside of the starter could have seized. Not in the conventional way, but by having parts shatter and wedge themselves internally, creatng  a lock on the flywheel IF the sprag has engaged the clutch during a ride. My buddy's starter could not be rebuilt.
However, i would remove the engine cover and starter to get a better idea of what is going on inside.

Sorry if i am not much help,
RB

If it's the "starter turns, engine does not" sort of problem, it may well be the bit the sprag engages with.

I had a similar problem with mine, until Desmoto diagnosed it as the gear/engagement bit the sprag sits being worn.

I've also heard tell that you can fix it by tightening the spring on the sprag. Carefully take the sprag spring apart, snip about 1 cm off it and reattach.

More details on that can be found here: http://ccrma.stanford.edu/~peer/Duc/duc-spragSpring.html

If the sprag has been replaced (with a new good unit) and does not function now I would look for something else wrong. no way a sprag should go bad that fast.
I would pull it apart and look for something assembled wrong or a part failure.
I have seen the starter idler gear seize to its shaft.
starter motor have the magnets fall off the housing
starter freewheeling gear be damaged from running it loose for too long.

happy hunting

Thanks gang! Cool new board and already so much help! wt:

Ok to clarify.
I press the starter button, solenoid closes and starter motor turns. All gears spin & in the right direction.

Previous sprag lasted about 500K's (which was a new part).
New sprag lasted about 15 starts and now it mostly slips, sometimes it grabs/turns for about 1/4 of a sec (the clutch jingle gives it away). But it never holds on to actually turn the crank/engine over. Not even with the plugs out. (I can freely spin the engine by hand with the plugs out.)
This same Sprag did turn/start the engine over about 15 times, now it won't.

When I was replacing the sprag i did notice some wear on the rise of the gear (the one that it make contact with), as DrunkenMonkey pointed out. I'm not sure if this is the problem as it DID start with the current sprag, but as I said gave up after about 15 starts.
I will see how much it is to get this gear. Hopefully some one is parting out a wrecked 900SS or I will order the part here in Aus.

In the interim I will remove cover, take photos, cut spring by 1cm and re-assemble. See how that goes.

Thank you all, for your advice so far.

Anyone else have an idea?

Was there any obvious wear on the inside or outside surfaces the sprag cams bear on when you had it apart?

You don't happen to be running some super slick friction modified oil in in now you've satsfied you dry clutch envy are you? The sprag needs a little friction to rotate the cams so they "jam up" to work - if the bearing surfaces are ok, I'd try shortening the spring around the sprag segments - it's an intertwined long skinny spring, just carefully pull the overlapping ends apart, then re-entwine them with 4 or 5 mm more overlap.

big

Hi big,
Im assuming your asking if there was obvious wear on the previous sprag... hard to say as it feel out in bits! There was no wear on the flywheel side of the flywheel landing, but there was a little wear on the gear rise (the other part the sprag grabs at).
No too much fancy oil, just Motorex 4T which apparently is recommended for this bike. No fancy mixes or other additives either.

Will def try to shorten the spring on current sprag and see how it goes. Might do a new tut with it too. Try to help others.

Cheers - Chris

Hi DMF'rs, *update*
Revisiting this thread o' mine.
Shortened spring on Sprag, no luck. It grabs the the start gear but slips the mintute compression builds, so it never rotates crank past compression, then it just stuters.
Ive decided that the wear on the starter gear is just too much. So i will be trying to solve this by buying a new starter gear. 

If anyone is wrecking or has parts for a 1995 900cc SuperSport 2v belt drive, please let me know. 

Alternatively does anyone have another solution for this problem. 
- Chris

**SOLVED**

Purchased a used (near new) starter gear and fitted it all up. Bike starts first go. Old starter gear was simply too far worn. Simptons included the stuterring of the bike trying to start. Its all good now.
Thanks to Gil for the part. - Chris

Hello-- I searched this topic and came across this thread.
It seems I'm having the same problem...starter spins, but motor will not turn over/start.
Can someone explain exactly how to modify the starter clutch/sprag?  A new sprag bearing is $200!!
Clicked the link, but there are no specific instructions on where to cut, how much to cut off the sprag spring.
It may be clear once I get the flywheel off, but the more info I have beforehand the better.
THANKS!

Quote from: pjd on October 01, 2008, 10:48:26 AM
Hello-- I searched this topic and came across this thread.
It seems I'm having the same problem...starter spins, but motor will not turn over/start.
Can someone explain exactly how to modify the starter clutch/sprag?  A new sprag bearing is $200!!
Clicked the link, but there are no specific instructions on where to cut, how much to cut off the sprag spring.
It may be clear once I get the flywheel off, but the more info I have beforehand the better.
THANKS!

A link:
http://www.mad-ducati.com/Technical/StarterSpragClutch/SpragClutch.html